Tucker Kern
M.S. FinalMay 13, 2014, 11:00 AM
Scott Bioengineering Odyssey Design Studio
Design of Integrated On-chip Impedance Sensors
Abstract: In this thesis two integrated sensor systems for measuring the impedance of a device under
test (DUT) are presented. Both sensors have potential applications in label-free affinity biosensors
for biological and bio-medical analysis. The first sensor is a purely capacitive sensor that operates
on the theory of capacitive division. Test capacitance is placed within a capacitive divider and
produces an output voltage proportional to its value. This voltage is then converted to a time-
domain signal for easy readout. The prototype capacitive sensor shows a resolution of 5 fF on
a base of 500 fF, which corresponds to a 1 % resolution. The second sensor, a general purpose
impedance sensor calculates the ratio between a DUT and reference impedance when stimulated
by a sinusoidal signal. Computation of DUT magnitude and phase is accomplished in silicon via
mixed-signal division and a phase module. An automatic gain controller (AGC) allows the sensor
to measure impedance from 30 Ω to 2.5 MΩ with no more than 10 % error and a resolution of
at least .44 %.
Prototypes of both sensing topologies were implemented in a .18 μm CMOS process and their
operation in silicon was verified. The prototype capacitive sensor required a circuit area of .014
mm2 and successfully demonstrated a resolution of 5 fF in silicon. A prototype impedance sensor
without the phase module or AGC was implemented with a circuit area of .17 mm2 . Functional
verification of the peak capture systems and mixed-signal divider was accomplished. The complete
implementation of the impedance sensor, with phase module and AGC, requires an estimated .28
mm2 of circuit area.
test (DUT) are presented. Both sensors have potential applications in label-free affinity biosensors
for biological and bio-medical analysis. The first sensor is a purely capacitive sensor that operates
on the theory of capacitive division. Test capacitance is placed within a capacitive divider and
produces an output voltage proportional to its value. This voltage is then converted to a time-
domain signal for easy readout. The prototype capacitive sensor shows a resolution of 5 fF on
a base of 500 fF, which corresponds to a 1 % resolution. The second sensor, a general purpose
impedance sensor calculates the ratio between a DUT and reference impedance when stimulated
by a sinusoidal signal. Computation of DUT magnitude and phase is accomplished in silicon via
mixed-signal division and a phase module. An automatic gain controller (AGC) allows the sensor
to measure impedance from 30 Ω to 2.5 MΩ with no more than 10 % error and a resolution of
at least .44 %.
Prototypes of both sensing topologies were implemented in a .18 μm CMOS process and their
operation in silicon was verified. The prototype capacitive sensor required a circuit area of .014
mm2 and successfully demonstrated a resolution of 5 fF in silicon. A prototype impedance sensor
without the phase module or AGC was implemented with a circuit area of .17 mm2 . Functional
verification of the peak capture systems and mixed-signal divider was accomplished. The complete
implementation of the impedance sensor, with phase module and AGC, requires an estimated .28
mm2 of circuit area.
Adviser: Tom Chen
Co-Adviser: N/A
Non-ECE Member: Stuart Tobet
Member 3: Ali Pezeshki
Addional Members: N/A
Co-Adviser: N/A
Non-ECE Member: Stuart Tobet
Member 3: Ali Pezeshki
Addional Members: N/A
Publications:
Kern, T.; Chen, T., "A 0.18 μm integrated impedance sensor using a novel mixed-signal divider and automatic gain control," Circuits and Systems (ISCAS), 2014 IEEE International Symposium on, (in press)
Kern, T.; Chen, T., "A low-power, offset-corrected potentiostat for chemical imaging applications," Circuits and Systems (LASCAS), 2013 IEEE Fourth Latin American Symposium on,
Kern, T.; Chen, T., "A 0.18 μm integrated impedance sensor using a novel mixed-signal divider and automatic gain control," Circuits and Systems (ISCAS), 2014 IEEE International Symposium on, (in press)
Kern, T.; Chen, T., "A low-power, offset-corrected potentiostat for chemical imaging applications," Circuits and Systems (LASCAS), 2013 IEEE Fourth Latin American Symposium on,
Program of Study:
ECE534
ECE571
ECE513
ECE536
ECE580A4
ECE658
ECE699
N/A
ECE534
ECE571
ECE513
ECE536
ECE580A4
ECE658
ECE699
N/A